1. Field of the Invention
This invention relates to a method for producing an oxygen-containing aromatic compound by oxidizing an alkyl group of an aromatic compound possessing at least one alkyl substituent group.
2. Description of the Related Art
Heretofore, a method for producing an aromatic carboxylic acid, for example, by oxidizing an alkyl group of an aromatic compound possessing at least one alkyl substituent has been carried out in a liquid phase using a lower alkanoic acid typified by acetic acid or water as a solvent in the presence of a bromine compound or a compound of such a transition metal as cobalt or manganese.
JP-A-2000-103,758 discloses a method for producing an aromatic ketone by subjecting an aromatic compound possessing Rxe2x80x94CH2xe2x80x94 group to liquid-phase oxidation. The heteropoly acid which is used in this production is such a heteropoly acid as lacks a defective structure site and the production is aimed at an aromatic ketone. JP-A-08-53,391, JP-A-09-169,694, and JP-A-09-286,756 disclose methods for producing an aromatic carboxylic acid in an aqueous medium using as a catalyst a compound having a transition metal incorporated in a heteropoly acid skeleton possessing a defective structure site. JP-A-09-286,757 discloses a method for producing an aromatic carboxylic acid by using a catalyst obtained by thermally treating a heteropoly acid ion possessing a defective structure site and a transition metal salt in an aqueous medium at a temperature of not lower than 100xc2x0 C. JP-A-11-1,447 discloses a method for producing an aromatic carboxylic acid in an aqueous solution in the presence of a heteropoly acid or a salt thereof or a transition metal not incorporated in a heteropoly acid. Though these disclosures indicate use of heteropoly acid catalysts in the production of aromatic carboxylic acids, they have no specific mention of a heteropoly acid catalyst which possesses two defective structures.
This invention has for an object thereof the provision of a method for producing an oxygen-containing aromatic compound by oxidizing an aromatic compound possessing at least one alkyl substituent while avoiding use of a corrosive bromine ion as a catalyst and nevertheless using a catalyst so stable as to shun decomposition and also reusable even in an oxidizing atmosphere.
The object mentioned above is accomplished by a method for the production of an oxygen-containing aromatic hydrocarbon by the oxidation of an alkyl group of an aromatic compound possessing at least one alkyl substituent with a molecular oxygen-containing gas, which comprises effecting the oxidation by the use of a catalyst having a hetero atom formed of at least one element selected from among phosphorus, silicon, and germanium and a poly atom formed of at least one element selected from among molybdenum, tungsten, vanadium, and niobium and comprising a heteropolyoxometalate anion possessing two defective structure sites and at least one element selected from the group consisting of the elements of Periods 4xcx9c6 of Groups IB, VA, VIIA, and VIII in the Periodic Table of the Elements.
The method of this invention is enabled, by oxidizing an aromatic compound possessing at least one alkyl group in the presence of a catalyst not entailing corrosion of apparatus and operating effectively in the least possible application rate, to produce a useful oxygen-containing aromatic carbonyl compound and/or aromatic carboxylic acid.